Bonded aggregate structures and production thereof

ABSTRACT

Bonded aggregate structures, processes for their production, improved wall, floor and ceiling panel structures laminated with bonded aggregate and methods for their production are provided. The structures are made using a workable quick-setting non-toxic non-ammoniacal mixture of magnesium oxide, aluminum oxide, aggregate and mono aluminum phosphate acidic solution. The panel structures, especially for building purposes and the like, can be made in various forms ranging from low density to load-bearing forms which may be refractory, insulative, heat reflective, light weight, labor and energy conserving, etc.

TECHNICAL FIELD

This invention relates generally to bonded aggregate structures andtheir production and to improved building (wall, floor and ceiling)panel structures and the like laminated with bonded aggregate andmethods for their production.

BACKGROUND ART

Bonded aggregate structures are well known for refractory purposes (e.g.U.S. Pat. No. 3,285,758) and for outdoor load-bearing and road repairuse (e.g., U.S. Pat. No. 4,059,455). The mixtures used for forming theknown structures require a high content of ammonium phosphatecomponents. Such use is impractical and even hazardous for manypurposes, particularly indoors or at building sites where goodventilation is unavailable to remove the high concentration of gaseousammonia generated by the bonding reaction.

It is therefore an object of the present invention to provide bondingaggregate structures and means for their production which avoid thedisadvantages of the prior art structures and processes.

It is also an object of the invention to provide bonded aggregatestructures in any of a variety of densities, compressivities, shapes,reflectivities, insulative and energy transfer qualities, fire resistantproperties and the like.

It is another object of the invention to provide economical means forimproving the energy efficiency of panel structures and the like as, forexample, in furnaces, stoves, heaters, radiant heat panels, wall, floorand ceiling surfaces, building and room dividers, warehouse and storagespaces, heating and processing zones and the like.

It is still another object to provide means for the fast repair,retrofitting and/or construction of insulative or load-bearing surfaces,structures and the like, advantageously at ambient temperature.

These and other objects, features and advantages will be seen from thefollowing detailed description of the invention.

DISCLOSURE OF THE INVENTION

The invention in one aspect is in bonded aggregate structures obtainedat ambient temperature by establishing a workable aggregate mixturewhich undergoes an exothermic reaction, working the mixture into apredetermined form prior to setting, and allowing the worked form to setinto a rigid structure. The workable mixtures of the invention areconstituted with magnesium oxide, aluminum oxide, aggregate and aqueousmono aluminum phosphate acidic solution; optionally with compatiblestructural fibers such as glass fibers and filaments. While the qualityand proportions of the components are not particularly critical, theweight ratio of aluminum oxide to acidic solution (expressed as 50%solution with a weight ratio P₂ O₅ :Al₂ O₃ of about 4) suitably is fromabout 1:1 to about 1:3, the weight ratio of magnesium oxide to aluminumoxide is from about 1:1 to about 1:6, and the quantity of acidicsolution relative to the total mixture is sufficient prior to setting toimpart lubricity (that is, smoothness and uniformity) to the mixture.The setting time of the mixture can be varied as desired. By increasingthe relative proportion of aluminum oxide, the setting time isincreased.

The magnesium oxide used is a dry dead-burned particulate magnesia. Atypical chemical analysis and mesh size for magnesia may be thefollowing:

    ______________________________________                                                 Standard                                                             Oxide    Mesh Size                                                            ______________________________________                                        SiO.sub.2                                                                              4.6%           +48    0.2%                                           Fe.sub.2 O.sub.3                                                                       2.7           +100    6.5                                            Al.sub.2 O.sub.3                                                                       1.2           +200    21.6                                           CaO      4.2           +325    17.7                                           MgO      87.3          -325    54.0                                           (Bulk density, g./cc., 3.16)                                                  ______________________________________                                    

The aluminum oxide is a dry alumina powder or calcined alumina for whicha typical analysis may be the following:

    ______________________________________                                               Oxide                                                                  ______________________________________                                               SiO.sub.2                                                                           0.03%                                                                   Fe.sub.2 O.sub.3                                                                    0.03                                                                    Na.sub.2 O                                                                          0.13                                                                    Al.sub.2 O.sub.3                                                                    99.8                                                             ______________________________________                                    

The aggregate is any suitable siliceous aggregate or mixture of suchaggregates having an average density ranging from light to heavydepending on the intended use. The size range of the aggregate is notcritical and suitably may be from under 1/16 inch to over 1/2 inch.Examples of aggregate materials are cellular and non-cellular materialssuch as sand, stone, refractory aggregates, silica aggregates and rareearth materials, pea gravel, expanded perlite and vermiculite, volcanicglass, volcanic ash, pumice, glass beads, silica aggregates and thelike. In applications where high mass is a problem, the use of cellular,low density aggregate is preferred, the density for strength and lowweight advantage preferably being in the range from about 5 to about 15pounds per cubic foot. Glass beads, perlite and vermiculite arepreferred cellular low density aggregates. For high density bondedaggregate structures, an aggregate such as stone, refractory aggregate,sand or gravel is preferred. The aqueous mono aluminum phosphate acidicsolution can be varied in concentration and amount used such that it isequivalent for purposes of imparting lubricity and reacting, to analuminum phosphate, 50% solution, technical grade, having the followingtypical properties:

    ______________________________________                                        Formula:    Al(H.sub.2 PO.sub.4).sub.3.XH.sub.2 O (in aqueous solution)       Molecular Weight:                                                                         318 for AL(H.sub.2 PO.sub.4).sub.3                                Description:                                                                              A clear, water-white solution                                     Typical Analysis:                                                                         P.sub.2 O.sub.5 :                                                                           33.5%                                                           Al.sub.2 O.sub.3 :                                                                          8.0%                                                            P.sub.2 O.sub.5 /Al.sub.2 O.sub.3 :                                                         4.19                                                            Al.sub.2 O.sub.3 /P.sub.2 O.sub.5 :                                                         0.24                                                            ALPO.sub.4 :  19.0%                                                           H.sub.3 PO.sub.4 :                                                                          30.9%                                                           Free H.sub.2 O:                                                                             40%                                                             Water of Hydration:                                                                         10%                                                 Physical Properties:                                                                      pH (1% solution):                                                                           2.5                                                             Specific Gravity:                                                                           1.47 @ 25/15.5° C.                                       Baume:        46 @ 25° C.                                              Viscosity:    35-90 centipoise                                                Loss at 110° C.                                                                      48-50%                                                          Miscibility w/water                                                                         Total                                               ______________________________________                                    

An advantage of the instant mixtures is that they can be establishedunder cold weather conditions. No external heat is required. Thereaction which takes place upon mixing the components is exothermic. Thesetting time varies depending on the relative quantities of thecomponents. For example, the setting time of the mixture is about 4 to 6minutes when the weight ratio MgO:Al₂ O₃ is 1:1 and can be extendedcorrespondingly as this ratio is decreased. Prior to mixing, the dry andwet components are kept separately. For purposes of mixing, thecomponents are then brought together in any suitable way to provide auniform workable mixture. Conveniently for this purpose, the drycomponents magnesium oxide, aluminum oxide and aggregate can beformulated in a single package or lot separate from the acidic solution.The latter, contained in an appropriate quantity as a single unitpackage or lot, can then be combined with the dry components at the siteof mixing and forming. The resulting mixture, while still workable isthen placed, shaped, compacted, etc., by conventional means, into asuitable form or cast, and allowed to set until rigid, for purposes ofrepair, retrofitting or construction. The form used can be a cavity orbreak in a road surface or bridge, a specially made construction form, abuilding template or modular form, an open space within a wall or flooror ceiling, the wall surfaces of a chimney or furnace, a panel adaptedto receive a covering laminate or layer of settable material, or othersimilar form. An important advantage of the instant bonded aggregatestructures is that they are non-ammoniacal so that during mixing,forming and setting no special precautions need be taken to vent thearea of ammonia fumes. Other advantages in this regard are that theformulations are temperature insensitive, can be made to have high earlystrength, and given the benefit of the present teaching, can be adjustedwithin wide limits to suit the particular requirements of each job.Thus, the formulation can be varied for setting to a fast or slowrock-hard set by varying the ratio of alumina to magnesium oxide; forlow density (less than about 15 pounds per cubic foot) or high density(more than about 15 pounds per cubic foot), and for various degrees ofwetness, looseness, plasticity, stickiness, adhesion, etc., as desired,without special knowledge, by those skilled in the art. For example, bya procedure described below in greater detail, a good high density, loadbearing ceramic material having early high strength can be made with thefollowing components:

    ______________________________________                                                        Parts By Weight                                               ______________________________________                                        Magnesium oxide   1.5                                                         Aluminum oxide    1.5                                                         Sand              3                                                           Mono aluminum phosphate,                                                      50% acidic solution                                                                             3                                                           ______________________________________                                    

One preferred aspect of the invention is a method of improving theenergy efficiency of a room panel or zone-confining panel having afacing surface and an energy-transmissive backing surface. The termsroom panel and zone-confining panel as used herein are meant to includewall or floor or ceiling members of buildings; work-station panels,dividers, carrels, stalls, booths, etc.; radiant heat panels, fire wallsand false ceilings, panel and wall members of stationary objects such ashoods, stoves, furnaces, vats, boilers, animal shelters, brooders,silos, storage tanks, processing chambers; and the like. The method ofimproving the energy efficiency of such panels includes the steps oflaminating the backing surface, and allowing the thus laminated mixtureor cover to set until hard and thereby become rigidly attached to thebacking surface. Energy efficiency is realized in that panels laminatedaccording to the invention become heat-insulative, especially panelsthat are laminated with mixtures containing cellular aggregates such asglass beads, expanded perlite, etc. In the latter case, the K-factor ofthe resulting bonded aggregate cover is comparable to that of thecellular aggregates per se. When the cover includes a mix of cellularand non-cellular aggregate, certain advantages are seen such as enhancedheat content or capacity whereby the cover has a so-called flywheeleffect with respect to retention of heat or energy level over prolongedperiods, which serves to avoid precipitous changes in temperature withinthe confines of the covered panel or panel enclosure. Advantageously,the cover also serves as an acoustical insulator. It will be realizedthat the cover for the panel can be varied in its coverage of the paneland its thickness. Thus, the cover will ordinarily be completelyco-extensive with the panel. The cover can be uniform or non-uniform inthickness, as desired. To assist in strengthening the attachment of thelaminate to the cover, anchoring means which may be conventional can beused such as lathing strips, fingers, tie rods, perforations, and thelike, spaced at intervals on the panel. A preferred panel embodiment ofthe invention is an overhead or ceiling panel member and preferably aradiant heat panel, laminated according to the method of the invention.A preferred method embodiment comprises the step of anchoring thelaminated mixture to the radiant heat panel by pre-formed mold definingrelief surface means in the panel, presently to be described.

Referring to the accompanying drawing of a preferred radiant heat panelor space heater panel, according to the invention,

FIG. 1 is a view showing the facing surface; and

FIG. 2 is a cross-sectional view of a panel taken on line 2--2 of FIG. 1showing the panel and its cover of laminated bonded aggregate structure.

As seen in FIGS. 1 and 2, the radiant heat panel 10 has an exposedsurface 11 and a congruent backing surface 12 to the latter of which abonded aggregate 13 is attached. The attachment is favored and preventedfrom lateral dislodgement by mold forming relief means or sunk reliefanchor means 14. A support system 20, suspended from overhead as fromthe ceiling (not shown) of a building or room by a cable or chain 21attached to the panel is used to maintain the panel 10 steady at apredetermined position above the floor for purposes of heating the spacewithin the room. Further cable segments 22 support a reflector 23 whichin turn by attachment to cable segments 24 and mounting base 24a supporta gas burner 25 and pilot 26. The latter burner and pilot unit isserviced by a temperature controller 30, gas supply line 31, and burnerand pilot lines 32 and 33. In a preferred embodiment, the panel 10 is 24gauge steel, 4 feet in diameter with one foot center-to-center radialspacing of the circumferential anchor means 14. The bonded aggregatecover 13 is about 1-2 inches thick. The heating unit uses a burner ratedat 15,000 BTU. Air temperature control is adjustable from 78° to 110° F.

In a preferred procedure, the backing surface 12 of the panel islaminated to a depth of about 1 to 2 inches using a uniform mixture ofthe following components:

    ______________________________________                                                             Percent By Weight                                        ______________________________________                                        Magnesium oxide                                                               (BRI® dry burned MAGNESITE BD87,                                          available from Basic Refractories                                             Cleveland, Ohio)       10                                                     Aluminum oxide, calcined                                                      (C-70 to C-75 FG, available from                                              Alcan Aluminum Corporation)                                                                          30                                                     Glass beads, cellular,                                                        (size distribution, 1/16" to 1/2",                                            available from Norton Chemical Co.)                                                                  30                                                     Mono Aluminum Phosphate, 50% aqueous                                          solution, (available from Stauffer                                            Chemical Co., Westport, Conn.)                                                                       30                                                     ______________________________________                                    

The dry ingredients are first mixed, and the solution is then added withthorough mixing at ambient temperature to provide a smooth mixture. Theresulting mixture is applied in a layer by troweling or other suitablemeans to the top of the radiant heat panel and allowed to set. Themixture sets to rock-like hardness in about 6 to 8 minutes. Thelaminated panel can be used immediately for radiating heat. Suprisingly,the savings in energy usage typically is 20 to 50% or more. Theincreased efficiency is seen by the fact that heat losses are minimizedsuch that to maintain a given temperature, the burner unit is activatedsubstantially less frequently then with prior art uncoated heaterpanels.

The lamination according to the invention can be advantageously doneusing a conventional panel 10 which lacks the relief shaped anchor means14. Optionally, the facing surface 11 of the cover 13 can be coated witha suitable light or heat reflective paint or similar coating. Theradiant heat panels of the invention are preferred for animal shelters,especially for brooder radiant heat panels used, for example, in raisingchicks.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A bonded aggregatestructure obtained by establishing a non-ammoniacal workable mixture ofmagnesium oxide, aluminum oxide, aggregate, and aqueous mono aluminumphosphate acidic solution, the weight ratio of aluminum oxide to acidicsolution (expressed as 50% solution with P₂ O₅ :Al₂ O₃ of about 4) beingfrom about 1:1 to about 1:3, the weight ratio of magnesium oxide toaluminum oxide being from about 1:1 to about 1:6, and the quantity ofacidic solution relative to the total mixture being sufficient prior tosetting to impart lubricity to the mixture; working the mixture into apredetermined form, and allowing the thus worked form to set into arigid structure.
 2. A structure according to claim 1 where the aggregateis cellular and has a low density in the range from about 5 to about 15pounds per cubic foot.
 3. A structure according to claim 2 where theaggregate comprises glass beads.
 4. A structure according to claim 2where the aggregate comprises perlite.
 5. A structure according to claim2 where the aggregate comprises vermiculite.
 6. A structure according toclaim 1 where the aggregate comprises a stone or refractory aggregate.7. A structure according to claim 2 made from a mixture containing byapproximate weight 10% magnesium oxide, 30% aluminum oxide, 30%aggregate and 30% acidic solution.
 8. A structure according to claim 7where the aggregate comprises glass beads.
 9. A process for producing abonded aggregate structure comprising the steps of establishing aworkable non-ammoniacal mixture of magnesium oxide, aluminum oxide,aggregate and aqueous mono aluminum phosphate acidic solution, theweight ratio of aluminum oxide to acidic solution (expressed as 50%solution with P₂ O₅ :Al₂ O₅ of about 4) being from about 1:1 to about1:3, the weight ratio of magnesium oxide to aluminum oxide being fromabout 1:1 to about 1:6, and the quantity of acidic solution relative tothe total mixture being sufficient prior to setting to impart lubricityto the mixture; working the mixture into a predetermined form; andallowing the thus worked form to set into a rigid structure.
 10. Aprocess according to claim 9 where the aggregate is cellular and has alow density in the range from about 5 to about 15 pounds per cubic foot.11. A process according to claim 10 where the aggregate comprises glassbeads.
 12. A process according to claim 10 where the aggregate comprisesperlite.
 13. A process according to claim 10 where the aggregatecomprises vermiculite.
 14. A process according to claim 9 where theaggregate comprises a stone or refractory aggregate.
 15. A processaccording to claim 10 made from a mixture containing by approximateweight 10% magnesium oxide, 30% aluminum oxide, 30% aggregate and 30%acidic solution.
 16. A process according to claim 15 where the aggregatecomprises glass beads.
 17. A method of improving the energy efficiencyof a room panel or zone-confining panel having a facing surface and anenergy-transmissive backing surface, which comprises the steps ofestablishing a workable mixture of magnesium oxide, aluminum oxide,aggregate and aqueous mono aluminum phosphate acidic solution accordingto claim 9, laminating the backing surface with the workable mixture toprovide a generally co-extensive energy conserving cover for the backingsurface, and allowing the thus laminated mixture to set until hard andthereby become rigidly attached to the backing surface.
 18. A methodaccording to claim 17 where the panel is a floor or wall member.
 19. Amethod according to claim 17 where the panel is an overhead or ceilingmember.
 20. A method according to claim 19 where the panel is a radiantheat panel.
 21. A method according to claim 20 which comprises the stepof anchoring the mixture to the panel by pre-formed mold defining reliefsurface means in the panel.
 22. A method according to claim 21 whichcomprises the step of removing the relief surface means subsequent tothe setting of the laminated mixture such that portions of the undersideof the laminated mixture are exposed.
 23. A radiant heat panel producedby the method of claim 20.